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phosphate question

Discussion in 'Advanced Strategies and Fertilization' started by john b., May 21, 2005.

  1. john b.

    john b. Junior Poster

    May 21, 2005
    Likes Received:
    Tom, I read a post of yours on another forum which you said " inhibition of plant growth ranges for po4 are over 5ppm", does this mean over 5 ppm of po4 will affect growth or other nutrient uptake rates? If so , is this even if all other nutients are in proper range and how much over 5ppm would cause issues? Thanks,
  2. Tom Barr

    Tom Barr Founder
    Staff Member Administrator Social Group Admin

    Jan 23, 2005
    Likes Received:
    Re: phosphate question

    That means many folks have gone to 5ppm.
    We do not know if anything causes issues above that.
    Why would anyone want to add more than that?
    Even a bad dosing error would not get over that.

    Every once in awhile, someone thinks the KH2PO4 is KN03.
    So it does happen but a water change brings it right back down.
    Otherwise you have to add so much it starts to effect the KH buffering system(maybe 7-20ppm).

    We add plenty for the plants at 1-2ppm.
    There is a level that causes issues, but it's very high and impractical to find out critically since it likely effects the CO2/buffering system rather than merely PO4 inhibition impacting uptake.

    Tom Barr

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